patch volume fraction

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  • Last Post 05 March 2019
Bibek Poudel posted this 14 February 2019

Hi, 

I am doing a simulation with two boxes like this: 

Here I have defined the top box to be fluid and bottom box to be solid. I am using multiphase VOF model and in the top box, I have patched the high viscous Silicon-liquid (viscosity= 1000 Pa.s ) to have volume fraction=1. I ran the my simulation for 1 second only where I rotated the frame of top box (i.e si-liquid fluid box). I was hoping as the viscosity of Si is too high, they would stick together. But after the simulation when plotted the contour of volume fraction of Si, it came out like this: 

It looks as if there is no Si left in majority of the portion. Why is it so? Can anyone please elaborate this? Also, can anyone help me find a process where I can make this Si attached to the upper box throughout the simulation? And is this because I rotated the frame? The speed was not that much though, it was just 1.57 rad/s. 

Thanks in advance, 
Bibek 

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kkanade posted this 15 February 2019

can you create a contour plot of vof just after you do patching and insert that image here. 

how did you rotate upper box? can you please insert images of cell zone setup. 

kkanade posted this 15 February 2019

also please let us know which models you are using. 

Bibek Poudel posted this 15 February 2019

Hi kknade, Thanks for replying. 

- The contour of VOF after I just patched is like this: 

 

I don't know why the contour is like this vertical area. And I used just the frame motion to rotate the upper box. The picture of cell zone setup is here: 

 

And I am using: Multiphase VOF, laminar, DPM injection model. If there is anything you want to ask, I am happy to provide additional info. 

Thanks,
Bibek

rwoolhou posted this 15 February 2019

That looks odd: I'd expect the whole top box to be red (vol frac of 1). Did you patch the fluid zone? What boundary conditions have you got on the silicon container?

Bibek Poudel posted this 15 February 2019

Yes, I patched the fluid zone. I also don't know why this happened. But when I tried patching without frame motion, it patched like this: 

 

Still when i inject just 1 particle for 1 second again the volume fraction contour changed to like this: 

It seems like my fluid are all splatted out. Why is this so? I am using viscosity of 1000 PaS. It should be sticking together, right? Right now I am not even using the frame motion. Still the volume fraction shows such drastic change in after 1 second. Could you please help me understand this? 

Thanks,
Bibek

Raef.Kobeissi posted this 17 February 2019

Silly question but are you sending us the contour before you ran the simulation or after you've run it for some time?

Raef Kobeissi

Bibek Poudel posted this 18 February 2019

No, That's fine. Actually, I have uploaded here the both volume fractions: before simulation and after simulation. Still this is before simulation: 

 

And this is after simulation: 

I have used very high viscosity; so I expected the fluid to stick around; but it seems like they got splattered away. All I did was rotated the frame of top box with just 1.57 rad/s for 1 second only. 

Can you please help me why this happened? 

Thanks,
Bibek

abenhadj posted this 18 February 2019

You said droplet? Which droplet? Can you run without frame rotation at first to see whether this droplet erase the patched VOF?

Best regards,

Amine

Bibek Poudel posted this 19 February 2019

Hi, I don't think I said droplet before but I am just injecting a iron particle in this fluid medium. And without rotation too, it changed like this: 

Before Simulation after patching: 

 

After simulation (just injection of 1 particle, no frame rotation, 1 second time, viscosity= 100 Pas): 

 

It changed like this. Can you please explain why this is happening? With that amount of high viscosity and no rotational force, shouldn't they stick together? 

Thanks,
Bibek

abenhadj posted this 19 February 2019

How is this droplet injected (sorry If I am using droplet instead of particle)? How big is the viscosity ratio? Which schemes are you currently using for VOF? Is gravity enabled? How big is the CFL number?

Best regards,

Amine

Bibek Poudel posted this 05 March 2019

I used the file injection to inject the particle. And I just used the patch volume after initialization to patch the liquid silicon to the container. The silicon has huge viscosity of 1000 Pas. And I am using 2-phase VOF model (I am not sure I answered you correctly here, what do you exactly want for scheme?). Anyway this is the setup: 

Thanks,
Bibek

abenhadj posted this 05 March 2019

I cannot follow sorry: either you provide a thorough description of your case and all stuff included in it otherwise we won't be able to help. Try to summarize a bit: What is the problem? What is included?

Moreover, try to track the mass of the secondary phase in the domain to see whether it is conserved or not.

Best regards,

Amine

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